The present invention relates to the field of small wheeled vehicles, and more specifically, it is directed to a drive assembly for a manually propelled wheelbarrow, driven without the use of a motor or electric power.
Laborers in a variety of industries frequently use wheelbarrows and carts to manually move heavy or awkward loads about a work site. For example, in commercial settings construction workers may use wheelbarrows to transport supplies, waste debris, mixed concrete, and other materials as needed from point to point. In private settings, landscapers and gardeners may use wheelbarrows to aid in transporting rocks, soil and potting material, and other tools from a supply location to a work site.
The wheelbarrow has been known in one form or another since early civilization. It generally consists of a carrying enclosure such as a tub or box supported by two parallel handles, the handles being supported by the axis of a wheel serving as a fulcrum on one end and being lifted and pushed by a person holding the opposing end. The single wheel allows the load in the tub to be pushed and easily maneuvered along the ground around challenging obstacles. The size of the load carried in this manner is limited by the ability of the person pushing the wheelbarrow to vertically lift the load mass and then to apply horizontal force to cause the wheelbarrow to roll about its wheel axis along the ground. The horizontal force required to move the loaded wheelbarrow can be increased by obstacles on the ground that impede the rolling action of the wheel (such as rocks, ridges, uneven ground, tools, etc.) or grades. Engines and motors have sometimes been added to the wheelbarrow structure to assist the wheelbarrow user in moving the wheelbarrow horizontally over these obstacles and grades by applying an additional, cooperative driving force to the wheels.
Other wheeled vehicles that are manually powered utilize the same basic principles as wheelbarrows. Such items as garden carts, trash disposal containers, and wagons all employ manual effort for moving the vehicle and may have more than one wheel. For example, U.S. Pat. No. 424,903, issued to Rogers, teaches a spring powered drive apparatus for a three-wheeled vehicle that utilizes a diamond-shaped spring compressed by use of a hand lever. U.S. Pat. No. 6,390,213, issued to Bleicher, discloses a self-propelled cart powered by motors that power independent drive wheels so that each wheel thus equipped with its own motor assists the user in moving the cart over rough or uneven surfaces. The motors are powered by electrical means such as batteries. U.S. Pat. No. 2,2918,133, issued to Ericsson, discloses a barrow or cart also propelled by a gasoline-powered engine driving a single front axle having dual wheels.
Such modifications as adding engines and motors to the basic manual vehicle configuration greatly assist the user in moving heavy loads. However, there are a number of drawbacks to such arrangements. First, motors and engines are generally more expensive than the vehicle structure itself. Second, engines and motors are heavy and bulky and contribute to the weight of the combined vehicle structure and load. Third, the use of the engine or motor imposes a requirement to have a readily available source of fuel. In the case of an engine, gasoline or some other such volatile liquid must be provided; in the case of a motor, the battery must be recharged when it is depleted. In either case, the fuel source must accompany the vehicle or cart when using the apparatus in a remote area. Fourth, use of engines and motors increases the complexity of the apparatus. Engines in particular must be maintained and serviced at periodic intervals. Fifth, an engine is frequently noisy and creates air pollution from the exhaust fumes.
Thus, it can be seen that there is a need for a manual propulsion apparatus to assist the user in moving heavy loads around obstacles and up steep grades, the apparatus being inexpensive, simple to maintain, lighter than standard motors and engines, quiet, non-polluting, and requiring a readily available or renewable source of fuel. It can also be seen that such technology should be available to retrofit existing vehicles to reduce the cost of redundantly purchasing a new vehicle having the technology built-in to the vehicle.